1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing a semiconductor device, for example, a metal oxide semiconductor (MOS) transistor.
2. Description of the Related Art
With full use of a microfabrication technology, with times, it becomes possible to manufacture semiconductor devices while achieving downsizing without decreasing performance thereof. This tendency is also found in semiconductor elements having high driving performance, and hence a reduction in on-resistance per unit area has been pursued by making full use of the microfabrication technology. However, in fact, a lowering of a withstanding voltage, which is caused by miniaturization of elements, hinders further enhancement of the driving performance owing to the microfabrication technology. In order to overcome the trade-off between the miniaturization and the withstanding voltage, there have been proposed elements having various structures, and the trench gate MOS transistor can be nominated as a mainstream structure at present in the field of power MOS field effect transistors (FETs) having a high withstanding voltage and high driving performance.
Among doubled-diffused MOS (DMOS) transistors having a high withstanding voltage and high driving performance, the trench gate MOS transistor has the highest scale in integration (for example, see JP 01-310576 A).
The trench gate MOS transistor shows extremely excellent performance as an element itself, however it is disadvantageous when being mounted on a chip together with other semiconductor elements since the trench gate MOS transistor has a vertical MOS structure, in which current flows in a depth direction of a substrate, and an entire rear surface of a semiconductor substrate is an electrode.